Many patents have been obtained in the general field of footwear having soles that enable the user to obtain traction on surfaces that might be classified as slippery. Specifically, golf shoes are well-known in which metal studs are embedded in the sole of the shoe, and those studs extend outwardly from the bottom surface of the sole for a considerable distance. As a consequence, when such golf shoes are worn on sod, they readily penetrate the sod to such a depth that when the golfer exerts pressure on the shoe sole, the footwear will remain fixed in position on the sod despite a substantial torque being applied by the golfer as he turns during the golf shot.
Thus, a substantial industry has been developed for golf shoes. For example, in U.S. Pat. No. 3,760,514 a golf shoe is disclosed having a tungsten carbide insert in the sole. The insert extends outwardly to provide a wear resistant, spiked shoe sole particularly adapted for use on golf shoes. The spike can be molded integrally with a sole or heel.
It has also been recognized, however, that a golfer will at times walk on hard, compacted surfaces as well as sod. Thus, in a patent such as U.S. Pat. No. 4,561,197, a golf shoe is disclosed having receptacles for the spikes embedded in the shoe's outsole to relieve the spike-produced pressure points or zones that result from walking or standing on a hard surface with a conventional golf shoe. Consequently, the prior art has recognized a problem with golf shoes, which may be highly serviceable when the golfer is walking on sod, but are unstable and uncomfortable when the golfer is walking a hard surface, such as cement or asphalt.
However, it will likewise be apparent that while golf shoes may be adequate for walking on sod, and perhaps even useful when walking on a compacted surface, they are not serviceable for walking on other types of surfaces where there is a low efficient of friction between the footwear sole and the base surface. Illustrative of such surfaces are ice, sleet, grease or other hazardous surfaces. In designing a walking or running shoe, even if such slippery surfaces are encountered only intermittently, the wide variety of spiked shoes that have been developed for golfers are woefully inadequate on such surfaces.
As a consequence, when a runner is running on a variety of surfaces in a normal day's exercise, e.g., going from grass, to cement, to a patch of grease, to a patch of ice, the shoes presently available, and in particular those that are directed to the highly developed state-of-the-art relating to golf shoes, are not adequate.
It is, therefore, a primary object of the present invention to provide a sole for footwear that will be serviceable over a wide variety of surfaces, regardless of the hardness of those surfaces and the coefficient of friction between those surfaces and the bottom of the footwear soles.
It is a secondary object of this invention to provide such a sole that is able to be used not only in permanent footwear, but which is also suitable for application to existing footwear in order to convert that footwear into shoes suitable for running or walking on a wide variety of surfaces.